Analyses of phase differences from surface electrocardiogram recordings to distinguish the origin of outflow tract tachycardia

paroxysmal atrial tachyarrhythmias (AT). These drugs are effective in unmasking the electrocardiographic (ECG) pattern of Brugada syndrome. We determined the prevalence of Brugada-type ECGs with class IC antiarrhythmic drugs in patients with paroxysmal AT but no syncopal episodes and familial histories for sudden death. Methods: This study enrolled 425 consecutive AT patients who showed no characteristic ST-segment changes. Most of these patients had paroxysmal atrial fibrillation. The patients took class IC antiarrhythmic drugs to inhibit the arrhythmias. The drugs include flecainide (n 223; 150-200 mg/day), pilsicainide (n 189; 150-200 mg/day), and propafenone (n 13; 300-450 mg/day). We analyzed a total of 2,346 ECGs using a computerized ECG system (FDX6521). A Brugada-type ECG was defined as 0.2-mV elevation of the ST segment measured 20ms after the J point in leads V1 to V2, with a coved pattern. Results: No patients had Brugada-type ECGs before the antiarrhythmic drugs. The prevalence of an ECG of a 0.2-mV ST-segment elevation in leads V1 to V2 after the antiarrhythmic drugs was 27 (6.4%) of the patients. The prevalence of a typical coved-type aspect was 8 (1.9%) of the patients. These values were much greater than the reported mean prevalence (0.10.2%) of Brugada-type ECGs in Japanese healthy population. None of these patients had the documentation of ventricular tachyarrhythmias and syncopal episodes. Conclusions: The manifestation of Brugada-type ECGs by class IC antiarrhythmic drugs is not rare and not serious in patients with paroxysmal AT but no risk-stratifying factors for sudden death.